Doors or windows having one or more sliding panels are today in current use in dwellings. It is well known that with doors or windows of this type, when the sliding panel is in the closed position there is always a small space between the edge of the panel and the upright of the frame against which the sliding panels rests, or between the meeting uprights of the panels. This space often allows air to penetrate into the interior of the dwelling, and this increases heating costs, all the more so in severe climates.
Many weather-strips have been developed in the past for the purpose of eliminating this entry of air. These weather-strips are, however, deficient in many respects and, in most cases, they do not produce the anticipated results. For example, it is well known that one of the main properties of a weather-strip is that it shall be flexible and shall return to its original shape after a series of opening and closing cycles of the panel, so that it will provide a satisfactory seal and prevent the entry of air after several months of service. Now, conventional weather-strips tend to shrink, split or crack after a certain length of time, after which they only partly fulfill their function.
For the purpose of overcoming the problems of premature wear in existing weather-strips, consideration was given to the production of a weather strip which, when the sliding panel is in the closed position, is applied firmly to the frame of the panel in order to compensate for possible shrinkage of the weather-strip due to aging. However, this solution of the problem is far from ideal, since it increases the resistance of the sliding panel to displacement because of the increase in friction between it and the weather-strip.